`cmp:host {}` and `cmp:host some-other-selector {}` were not handled
consistently.
Note those should not match anything but are made equivalent to respectively
`:host(cmp)` and `:host(cmp) some-other-selector` to avoid breaking legacy apps.
- /deep/ is deprecated and being removed from Chrome
- >>> is semantically invalid in a stylesheet
- sass will no longer support either in any version of sass
-> use ::ng-deep in emulated shadow DOM mode
Because the deep combinator is deprecated in the CSS spec,
`/deep/`, `>>>` and `::ng-deep` are also deprecated in emulated shadow DOM mode
and will be removed in the future.
see https://www.chromestatus.com/features/6750456638341120
Misko Hevery
Victor Berchet
Jason Aden